An illuminating device for vehicles with a housing which is subdivided into multiple chambers is known from DE 44 21 306 C2. In each chamber, a light source and a reflector and a hologram element as an optical unit are arranged. The hologram element enables a desired visual effect which can for example be created through a stepped pattern. A disadvantage of previous illuminating devices is that when looking at the illuminating device, the reflector is arranged in the main radiation direction of the illuminating device behind the hologram element. To show the hologram created in a contrast-rich manner, it is desirable that the hologram element appears as dark or black as possible in the field of view. If there is a reflector behind the hologram element, then this is not possible. If, as shown in FIG. 9, the light source is arranged in a covered part of the lower part of the housing and the installation space for the illuminating device is limited in height and/or depth, then a reflector 3′ can usually only be arranged in such a way that it is at least partially in the field of view of the viewer and is partially covered by a hologram element 4′.